It is possible to stick a sheet of laminate directly to a bathroom wall but being a very thin sheet they would require a very flat surface in order to have any strength once fitted. To make life easier manufacturers bonded the laminate sheet to a stiff MDF or plywood core. This gave the panel structural rigidity and was more forgiving when it came to installation. A second sheet of laminate is bonded to the reverse side to stabilise the panel and prevent it from warping. Some versions of these panels are available with a tongue and grooved edge enabling them to be joined together to cover larger walls without the need for an obtrusive joining strip.
A recent development of the laminate panel involves utilising a waterproof foam core rather than a wood based core. This results in a lighter panel that is slightly flexible making manoeuvring the panel into restricted areas a little easier but both types of panel are quite large so they are a little more tricky to fit than the smaller PVC panels.